Robbert Robbertsz (Le Canu), born 1563 at Amersfoort, died after 1627 at Hoorn, Holland, was a teacher of navigation and the instructor of noted Dutch explorers, for example, Jacob van Heemskerck at Amsterdam from about 1586, and at Hoorn from 1610. At the close of his life he was living at Hoorn, earning his living by selling brandy.

Robbertsz was at first a member of the Frisian Mennonite congregation of Amsterdam. In 1589, when a schism arose in this congregation, dividing it into conservative Old Frisians and moderate Young Frisians, Robbertsz took the side of Lubbert Gerritsz, the leader of the Young (or Mild) Frisians; but soon after, probably by 1590, Robbertsz was banned even from this moderate group for his advanced ideas. Robbertsz defended himself in Verantwoordinghe oft ontschulddinghe (1592). With a few others he then founded the Robbert Robbertsz congregation, which had some adherents also in other Dutch towns (called Robbert-Robberts-volk). To this group also belonged Tymen Claesz Honich, who dedicated his hymnal Schriftuerlijck Lied-Boecxken to Robbertsz. It could not be ascertained how long this congregation existed, but it is fairly certain that it dissolved in a few years. Robbertsz himself seems to have left the Mennonites. In later years he called himself a "Neutralist," saying, "The church of Christ is a majestic cathedral with many doors, all leading to the center," with this metaphor expressing his idea that one church is as good as another. He is said to have had his children baptized in different Protestant churches.

Robbertsz wrote a number of pamphlets, some of which pertain to the Mennonites: in 1591-92 against Lubbert Gerritsz, in 1596 against Jacob Jansz Kist (that is, Jacob Schedemaker). In 1627 he published a booklet, Disputatie tusschen twie Huyslieden, which defended Jan Theunisz and attacked the preachers of the Amsterdam Waterlander congregation. He also attacked Reformed leaders such as Herman Moded. A reprint of some of his pamphlets and poems was published at Makkum in 1646.